This invention relates to a one-way clutch and a one-way clutch assembly, and particularly ones improved in compactness.
As one-way clutches used in drive units of electric devices and office devices, one as shown in FIG. 15 is known (JP patent publication 9-89011). It has roller receiving portions 24 formed in the inner-diameter surface of an outer ring 22 fitted on a shaft 21. On the bottom of each roller receiving portion 24, a cam surface 25 is formed so as to form a predetermined wedge angle between the cam surface 25 and the shaft 21. In the wide side of each roller receiving portion 24, a spring receiving recess 26 is formed.
A roller 27 is received in each roller receiving portion 24, and a spring member 28 received in each spring receiving recess 26 is pressed against the roller 27 to bias the roller toward the narrow side of the roller receiving portion 24 to stabilize the operation of the rollers 27.
On the outer ring 22, an outer annulus 29 is mounted so as not to rotate relative to the outer ring 22. The outer annulus 29 closes one end of the roller receiving portions 24 with one end face thereof. The other end faces of the roller receiving portions 24 are closed by an unillustrated lid member.
This one-way clutch is used with the outer annulus 29 mounted in a boss portion of a rotary member such as a gear. When the outer ring 22 rotates relative to the shaft 21 in a direction (shown by arrow A in FIG. 15), the rollers 27 will bite into the narrow sides of the roller receiving portions 24 and get locked, so that torque is transmitted with the shaft 21 and the torque limiter integrated. When the rotating direction is in reverse, since the rollers 27 move toward the wide sides of the roller receiving portions 24, the rollers 27 will get free, so that the one-way clutch idles and the torque is not transmitted.
In various devices in which this type of one-way clutch is used (paper feeding roller driving portions of printers/copiers, personal computers, portable information terminals, etc.), as the device bodies become compact, compactness of the one-way clutch is required. But in the conventional structure, since its outer diameter was necessarily larger than the diameter of the shaft, compactness was limited.
An object of this invention is to provide a one-way clutch that meets the requirement for compactness.
According to this invention, there is provided a one-way clutch comprising an inner member, an outer ring relatively rotatably mounted on the inner member, a rolling element mounted between the inner member and the outer ring, and a spring member for biasing the rolling element in one direction, a rolling element receiving portion having a predetermined wedge angle and a spring receiving portion communicating with the rolling element receiving portion being provided between the inner member and the outer ring, the spring member being received in the spring receiving portion, the rolling element being received in the rolling element receiving portion and biased by the spring member toward the narrow side of the rolling element receiving portion, wherein the inner member comprises a semi-columnar portion, and the rolling element receiving portion and the spring receiving portion are formed by the semi-columnar portion.
This one-way clutch is used with one end of the inner member coupled to a shaft. When the inner member, which is integral with the shaft, rotates relative to the outer ring in one direction, locking occurs due to biting of the rolling element, so that torque is transmitted, as in the prior art. When it rotates in the reverse direction, the rolling element gets free and idles, so that transfer of torque is shut off. Since the rolling element receiving portion and the spring receiving portion are provided in the inner member at the cut-out portion, the size of the one-way clutch can be reduced markedly compared with conventional devices.
The numbers of the rolling element receiving portions and the spring receiving portions (equal to the number of the rolling elements) are determined according to the load capacity. They are sometimes provided in only one set.
The semi-columnar member is formed with a cam surface for forming a wedge angle for the rolling element receiving portion, a roller stopper rib, and a spring seat for the spring member. The cam surface is formed by a cut-out surface parallel to a diametrical line of the inner member. The spring seat is disposed opposite to the cam surface relative to the roller stopper rib.
With this arrangement, the cam surface can be formed easily. Also, by the provision of the roller stopper rib, retraction of the rolling element beyond a predetermined range is prevented. This prevents the spring member from being collapsed by the rolling element during idling and prevents the rolling element from becoming locked during idling.
According to this invention, the inner member is provided with a coupling portion with a shaft, a radial bearing portion for the outer ring, and a flange having a larger diameter than the radial bearing portion and abutting one end face of the outer ring. The radial bearing performs the function of allowing smooth rotation of the inner member and the outer ring while keeping them in a concentric state. The flange prevents the inner member from coming out.
By providing an outer annulus on the outer ring, there is provided a one-way clutch assembly comprising a combination of the one-way clutch and the outer annulus. Also, by coupling a shaft to the coupling portion provided on the inner member, a one-way clutch assembly is provided which comprises a combination of the one-way clutch and the shaft.
In another embodiment of the present invention, the semi-columnar member is formed with a flat surface, and a cam surface for the rolling element receiving portion and a spring seat for the spring receiving portion are formed on the flat surface. With this arrangement, the inner member has a simple shape and is easier to manufacture.
In still another embodiment, a reinforcing plate is mounted on the flat surface, and the cam surface and the spring seat are formed on the flat surface. With this embodiment, the cam surface can bear the surface pressure applied from the rolling element during locking more securely. Thus, the allowable torque can be set to a higher value. Also, the inner member can be made by resin molding or sintering.
Also, the spring member may be provided with a restricting portion for restricting the retraction of the rolling element during idling. This prevents locking of the rolling member during idling.
Also, the inner member may comprise an integrated shaft member and a lid member and a radial bearing can be formed on the integrated shaft member and the lid member to support both ends of the outer ring.